PNNL

The Science                                 

Clean water is an essential resource for human life but is increasingly scarce in many areas of the world. Developing affordable, stable, and environmentally friendly ways to separate water and other chemicals with low energy consumption is essential. Researchers combined carbon nanotube porins (CNTPs), short sections of carbon nanotubes, with peptoids, a bio-mimetic polymer, to create a new class of membrane. They co-assembled the CNTPs, which exhibit properties similar to biological pores, with the peptoids to create biomimetic membranes with much greater stability than those made of lipids. Multiple experimental techniques confirmed the presence of CNTPs within the assembled peptoid sheets.

The Impact

Current polymer-based separations membranes are stable and relatively inexpensive, but they are significantly less selective and energy efficient than biological membranes. This new approach combines the efficiency, selectivity, and functionality of biological membranes via CNTPs with the enhanced stability of peptoid sheets. While this work represents a proof-of-concept for co-assembled CNTPs and peptoids, future work will employ the tunability of the different components to create more specialized functional membranes.

Summary

Generating affordable, clean water is essential for communities worldwide, especially in arid or underdeveloped regions. Robust and cost-effective polymer-based membranes dominate modern separations. Yet, their selectivity and energy efficiency are dwarfed by biological membranes with porin proteins like aquaporin, which facilitates water transfer across the membrane. CNTPs, which are solubilized with surfactant coatings, represent artificial water channels that can mimic an aquaporin. CNTPs co-assembled with lipid bilayers successfully demonstrate the same functionality of aquaporins in cell membranes. However, the relative fragility and low stability of the lipids represent vital drawbacks for potential industrial applications.

In this work, researchers tested the potential for co-assembling CNTPs with peptoids, a class of sequence-defined synthetic polymers that mimic peptides and proteins. After initial computational studies to confirm the energetic feasibility of assembly, researchers synthesized a novel biomimetic membrane from CNTPs and sheet-forming peptoids. The resulting nanomembranes are highly stable, robust, and self-repairable. These results demonstrate a compelling alternative strategy for the design and synthesis of biomimetic membrane materials.

PNNL Contact

James De Yoreo, Pacific Northwest National Laboratory, James.DeYoreo@pnnl.gov

Chun-Long Chen, Pacific Northwest National Laboratory, Chunlong.Chen@pnnl.gov

Funding

This project was supported by the Department of Energy, Basic Energy Sciences program, Division of Materials Science and Engineering at Pacific Northwest National Laboratory and Lawrence Livermore National Laboratory. This research used resources of the National Energy Research Scientific Computing Center, a Department of Energy Office of Science User Facility.